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Abstract

The linear wave instability of laminar mixed convective flow over an isothermal horizontal flat plate is studied analytically. The main flow and thermal fields employed in the stability analysis are treated as non-parallel. The system of linearized, coupled differential equations and their boundary conditions for the velocity and temperature disturbances constitutes an eigenvalue problem that is solved by a direct Runge-Kutta numerical integration scheme along with an iteration procedure. A filtering technique is employed to remove the truncation errors inherent in the numerical integration of the disturbance equations. Neutral stability curves and critical Reynolds numbers are presented for a range of values of buoyancy parameter covering both assisting and opposing flow situations for Prandtl numbers of 0.7 and 7.0. In general, it is found that the flow becomes less stable as the buoyancy force increases for assisting flow and more stable as the buoyancy force increases for the opposing flow. The regions of stable and unstable flows are also mapped out in a Grashof number vs Reynolds number plane. Finally, the present results from wave instability are compared with those from vortex instability.